Plural completion of wells



June 25, 1963 G. D'. THOMPSON ETAL PLURAL COMPLETION OF WELLS Filed Oct. 24,

INVENTCQRS GENE D. THOMPSON, DAVID E. SMINK ZMM ATTORNEY.

tion of Delaware Filed Get. 24, 1960, Ser. No. 64,636 4 Claims. (Cl. 166-46) This invention relates to the production of a plurality of productive earth formations through a single borehole, and more particularly to a method for complet ng a productive earth formation above the level of an existing productive earth formation that has been produced for a more or less extended period of time.

In connection with the production of oil and gas from productive earth formations, it has been the practice to cement a borehole liner, or casing, to the sides of a borehole, to perforate the casing so as to open fluid communication between the productive earth formation and the casing, and to produce the formation through a production pipe string or flow tubing. A production paclier between the flow tubing and the casing seals the portion of the well bore adjacent the earth formation from the upper portion of the annulus around the flow'tu-bing.

When it is later decided to produce a second productive earth formation that is above the level of the first productive earth formation, several techniques can be followed. A usual technique is to raise the flow tubing until the lower end thereof is above the level of the second productive earth formation, to lower a perforating gun through the flow tubing and, with the gun, to perforate the casing adjacent the second productive earth formation, and then to lower the flow tubing to its original position and reset the production packer. It is manifest that considerable expense must be entailed to carry out such an operation inasmuch as costly equipment must be brought to the well site to manipulate the flow tubing. Man festly, a simpler, less expensive technique for carrying out the operation is desirable.

In accordance with one aspect of the present invention, a perforating gun is lowered through the flow tubing to the level of the secondproductive earth formation. The flow tubing, the casing, and the surrounding sheath of cement are perforated, a pack-01f anchor is set in the flow tubing to blank oifthe perforations therein, the first productive earth formation is produced through the flow tubing and the pack-off anchor, and the second productive earth formation is produced through the annulus around the flow tubing.

Objects and features not evident from the above discussion will become apparent upon consideration of the following description when taken in connection with the accompanying drawing, wherein:

FIGS. 1 through 4 are schematic representations of an oil well installation illustrating various steps of the present invention.

With reference now to the figures generally, there is shown a borehole liner or casing pipe string 3 cemented to the wall of a borehole 1 with a cement sheath 5. A production pipe string 9, or flow tubing, coextends from the earths surface with the casing 3. The flow tubing 9 may include a gas lift mandrel 17 having a port 21. A blank-off plug '19 is used to seal off the port 21 from the bore of the flow tubing 9. The blank-off plug may be of the type illustrated at page 1098 of the Composite Catalog of Oil Field Equipment and Services, 24th edition (1960). A plurality of perforations 29 provide fluid communication between a first lower productive earth formation 28 and the bore of the casing 3. A production packer 27 between the lower end of the flow 3,095,038 Patented June 25, 1963 tubing 9 and the casing 3 seals off the portion of the bore adjacent perforations 29 from the annulus 10 around the tubing 9 to prevent flow of formation fluids from formation 28 up the annulus 10.

It will be assumed that the earth formation 28 has been produced for a more or less extended period of time and that a new productive earth formation 14 has been dis-covered above the level of earth formation 28. It now becomes desirable to produce earth formation 14 through the annulus 10 without vertically repositioning flow tubing 9. As illustrated in FIG. 1, a perforating gun 13 is lowered into the flow tubing on a wire line until it is adjacent earth formation 14, and is actuated to perforate tubing 9, casing 3, cement sheath 5, and to penetrate earth formation 14. The perforatinggun may be of the type utilizing either bullets or shaped charges. If desired, other types of perforators, such :as chemical or hydraulic perforators, may be used. If a shaped charge perforator is used, the strength of the explosive load in individual shaped charges and the spacing density of the charges on the perforating gu'n should be controlled. The shaped charges should be of sufficient strength to perforate the flow tubing 9, the casing 3, and the cement sheath' 5, and to penetrate the earth formation 14 to a reasonable depth. However, the strength of the charges and the density thereof should not be so great as to split the tubing. It has been found that 13 ounce shaped charges having a density of two per foot are usually satisfactory to perforate Z-inch, EUE tubing.

Either before or after the tubing and easing have been perforated, a plug 23 should be set in a landing recess 25 in flow tubing 9 to prevent fluid flow through the flow tubing between the levels of earth formations 14 and 17. After the formation 14 has been perforated to form perforations 15, the perforator 13 is withdrawn from the well. A swab 33 having a plurality of swab cups 35 is lowered into the flow tubing to a level above earth formation 14. The swab 33 is reciprocated in the flow tubing in order to initiate the flow of earth formation fluid from formation 14 as shown in FIG. 2. The annulus 10 may be opened to atmosphere so that well fluids standing in the annulus 10 before formation 14 is perforated, may be withdrawn from the annulus 10 through perforations 16 in flow tubing 9 and up flow tubing 9 along with formation fluids from formation 14. The purpose of the swabbing operation is to initiate flow of fluids from formation 14 and to reduce the hydrostatic head of fluids in annulus 10 to a level such that fluids may flow naturally from the flow tubing up the annulus. If, for some reason, it is desired to have the annulus 1!) closed off from the atmosphere, the swabbing operation will take a longer time inasmuch as some of the fluids from formation 14 must migrate up the annulus to displace annulus fluids, the level of fluids inthe annulus remaining the same.

The swab 33 is now withdrawn from the well. As shown in FIG. 3, a wire line retrieving tool 37 is lowered' into the flow tubing until it latches on to the fishing head of plug 23. The plug 23 is withdrawn from the well.

As shown in FIG. 4, a pack-off anchor 39 is set in the flow tubing 9 adjacent the earth formation 14 so that the annular sealing element 41 thereof is above the uppermost of perforations 16, and the annular sealmg element 43 is below the lowermost of perforations 16. The term pack-off anchor is used to designate an apparatus having an open bore, two or more annular sealing elements, and a setting apparatus adapted to seal off holes or perforations in a well pipe string at a predetermined level in the pipe string. The term is well known to the ant, and apparatus of this nature is described at page 4339 of the Composite Catalog of Oil Field Equipment and Services, 24th edition (1960).

9 a The apparatus is only schematically illustrated in FIG. 4.

The lower earth formation 28 may now be produced through the flow tubing 9 and the bore of the pack-off anchor 39. Earth formation 14 is produced through perforations 15 and through the annulus When it is desired to work over or stimulate the earth formation 14, certain jobs may be accomplished by working in the annulus without affecting the Well hookup, whereas in other jobs, the pack-off anchor 39 is withdrawn from the well by a conventional wire line retracting apparatus to permit circulation. In this latter type workover, the plug 23 is reset in the well, and acid, fracturing fluid, cement, or other liquid is injected into the earth formation through perforations 16 and and the portion of annulus 10 therebetween. When the operation is completed, blank-off plug 19 is removed and the injected liquid is circulated up the annulus 10 and out of the well. Blank-off plug 19' is replaced in mandrel 17, plug 23 is removed, and pack-off anchor 39 is replaced in the position illustrated in FIG. 4.

It has been found that it is possible to reduce the cost of initiating production from a second productive earth formation by as much as 75% utilizing the technique described above.

The invention is not to be restricted to the specific structural details or arrangement of parts herein set forth, as various modifications thereof may be effected without departing from the spirit and scope of this invention.

The objects and features of the invention having been completely described, what it is desired to claim is:

1. In a well comprising a cased borehole and a flow tubing string extending to a first productive earth formation for producing the formation, and packer means between the flow tubing and casing for preventing fluid flow up the annulus between the flow tubing and casing, a method of initiating production of a formation at a level above the packer comprising: perforating the flow tubing and casing at the level of a second productive earth formation above the packer and first productive earth formation; blanking off the perforations in the flow tubing with a pack-off anchor; producing the second earth formation through the annulus between the flow tubing and the casing; and producing the first productive earth formation through the flow tubing and the pack-off anchor.

2. In a well comprising a cased borehole and a flow tubing string extending to a first productive earth formation for producing the formation, and packer means between the flow tubing and casing for preventing fluid flow up the annulus between the flow tubing and casing, a method of initiating production of a formation at a level above the packer comprising: perforating the flow tubing and casing at the level of a second productive earth formation above the packer and first productive earth formation; blocking fluid flow through the flow tubing bore at a level between the first and second earth formations; swabbing the flow tubing above the second earth formation to flow earth formation fluids from the second earth formation andto reduce the hydrostatic head of fluids in the annulus between the flow tubing and the casing of the borehole until the hydrostatic head is sufliciently low to permit production of earth formation fluids through the annulus from the second earth formation; reopening the bore of the flow tubing between the first and second earth formation; and blanking off the perforations in the flow tubing with a pack-off anchor.

3. In a well comprising a cased borehole and a flow tubing string extending to a first productive earth formation for producing the formation, and packer means between the flow tubing and casing for preventing fluid flow up the annulus between the. flow tubing and casing, a method of initiating production of a formation at a level above the packer comprising: perforating the flow tubing and casing at the level of a second productive earth formation above the packer and first productive earth formation; lowering a tubular member in said flow tubing and sealingly positioning it in said flow tubing with its upper end sealed above and its lower end sealed below the perforations in said flow tubing to isolate the second earth formation from the first earth formation; producing the second earth formations through the annulus between the flow tubing and the casing; and producing the first productive earth formation through the flow tubing and the tubular member.

4. In a well comprising a cased borehole and a flow tubing string extending to a first productive earth formation for producing the formation, and packer means between the flow tubing and casing for preventing fluid flow up the annulus between the flow tubing and casing, a method of initiating production of a formation at a level above the packer comprising: perforating the flow tubing and casing at the level of a second productive earth formation above the packer and first productive earth formation; blocking fluid flow through the flow tubing bore rat a level between the first and second earth formations, swabbing the flow tubing above the second earth formation to flow earth formation fluids from the second earth formation and to reduce the hydrostatic head of fluids in the annulus between the flow tubing and casing of the borehole until the hydrostatic head is sufficiently low to permit production of earth formation fluids through the annulus from the second earth formation; reopening the bore of the flow tubing between the first and second earth formations; and lowering a tubular member in said flow tubing and sealingly positioning it in said flow tubing with its upper end sealed above and its lower end sealed below the perforations in said flow, tubing to isolate the second earth formation from the first earth formation.

References Cited in the file of this patent UNITED STATES PATENTS 

1. IN A WELL COMPRISING A CASED BOREHOLE AND A FLOW TUBING STRING EXTENDING TO A FIRST PRODUCTIVE EARTH FORMATION FOR PRODUCING THE FORMATION, AND PACKER MEANS BETWEEN THE FLOW TUBING AND CASING FOR PREVENTING FLUID FLOW UP THE ANNULUS BETWEEN THE FLOW TUBING AND CASING, A METHOD OF INITIATING PRODUCTION OF A FORMATION AT A LEVEL ABOVE THE PACKER COMPRISING: PERFORATING THE FLOW TUBING AND CASING AT THE LEVEL OF A SECOND PRODUCTIVE EARTH FORMATION ABOVE THE PACKER AND FIRST PRODUCTIVE EARTH FORMATION; BLANKING OFF THE PERFORATIONS IN THE FLOW TUBING WITH A PACK-OFF ANCHOR; PRODUCING THE SECOND EARTH FORMATION THROUGH THE ANNULUS BETWEEN THE FLOW TUBING AND THE CASING; AND PRODUCING THE FIRST PRODUCTIVE EARTH FORMATION THROUGH THE FLOW TUBING AND THE PACK-OFF ANCHOR. 